The present invention relates generally to inflatable cushions used in vehicle occupant restraint systems. More particularly, this invention relates to a cushion constructed from fabric in the form of two congruent equiangular polygons that may or may not share a common side and that, during the construction process, are superimposed in congruent fashion and joined along their respective coincident edge portions to form a polygon-shaped cushion.
An inflatable restraint cushion, or air bag, plays an important role in protecting the occupants of a vehicle from injury due to collision against the car body. Typically, the air bag is disposed within a supporting structure such as a dash panel, steering wheel, door panel, or other fixed portion of a car body in opposed or adjacent relationship to a seat in the vehicle. When inflated rapidly by the pressure of a reaction gas released from an inflator during a collision, the air bag serves as a protective barrier between the vehicle occupant and the steering wheel or other portion of the vehicle body against which the occupant might otherwise be thrown.
Air bags have been used in the past to protect both the vehicle operator and vehicle passengers. Systems for the protection of the vehicle operator are typically mounted in the steering column of the vehicle and utilize cushion constructions that deploy directly towards the driver. These driver-side air bags can be of a relatively simple configuration in that they function over a small, well-defined area between the driver and the steering column. Typically, driver-side air bags are circular or substantially circular in shape when viewed from the front or the back. Such circular air bags are frequently constructed by superimposing, aligning, and joining, along their respective coinciding edges, two generally circular fabric sections that are separately cut from a web or blank of air bag fabric. While such circular air bags are functionally effective, the circular shape of the front and back fabric sections or panels from which the air bags are constructed does not lend itself to the efficient utilization of fabric during the manufacturing process. Specifically, the arrangement of these circular pieces or panels on a given blank of air bag fabric does not result in efficient fabric utilization or yield. Fabric is wasted in producing such circular cushions since the circular templates do not have straight edges which can be aligned with the edges of the fabric blank or which can be juxtaposed in close proximity on the fabric to provide common or nearly common adjacent edges with minimal fabric waste between neighboring cut sections. Furthermore, because use of circular or other curved panels frequently results in oddly-shaped sections of fabric between neighboring cut panels, utilizing such inter-panel fabric to make other necessary parts of the air bag (e.g., various reinforcements, etc.) is often difficult.
As used herein, it is intended that the following terms be defined as indicated: The term xe2x80x9cpolygonxe2x80x9d is a plane geometric figure having n sides and n vertices. An equiangular polygon is a polygon in which all the angles comprising the vertices are equal. A regular polygon is an equiangular polygon in which all sides are of equal length. A convex polygon is one for which no side, if extended, will enter the polygon. Unless otherwise specified, the term xe2x80x9cpolygonxe2x80x9d shall refer to a convex, equiangular polygon. The term xe2x80x9ccongruentxe2x80x9d shall be used to mean capable of being superimposed so as to have a perimeter that is coincident throughout. The term xe2x80x9cfabricxe2x80x9d shall be used in a broad sense to describe any woven or non-woven fabric, film, polymer, combinations or composites thereof, or other suitable material from which the individual panels comprising an air bag may be constructed.
It is common, particularly in air bags designed for the protection of vehicle drivers, to find such air bags fabricated from the seaming or joining of two similarly-dimensioned circular panels along their respective perimeter edges after such circular panels have been cut from a blank of suitable air bag fabric and superimposed in congruent fashion. The instant invention provides for the use of relatively simple polygonal starting geometries for the fabric panels in order to reduce air bag fabric waste by reducing the quantity of fabric between the panels on a fabric blank. Additionally, fabric waste may be reduced because, when such polygons are used, the inter-panel fabric (which might otherwise have to be discarded when circular panels are used) tends to have a straight-sided shape from which the fabrication of other components needed for air bag construction (e.g., reinforcements and the like) may be more easily constructed, thereby saving on the area of uncut fabric blank that must be used in the construction process.
It has been found that fabric utilization can be significantly improved by substituting polygon shapes, and particularly equiangular polygons having n sides, where n is at least five, for the circular-shaped panels of the prior art. In one preferred embodiment, two such panels are individually cut and the cushion is constructed by superimposing the panels in congruent fashion (i.e., with coincident edges) and joining each of the n sides of one of the polygon-shaped panels to the respective coincident nth side of the other panel. In another preferred embodiment, a single panel is cut in the form of a pair of abutting, congruent n-sided equiangular polygons that share a common uncut side, i.e., a single, dual-lobed panel, having a perimeter comprised of 2nxe2x88x922 sides, in which each lobe resembles an n-sided polygon having nxe2x88x921 cut edges. This single piece panel may be folded about an axis that coincides with the shared uncut side to allow the lobes to be superimposed in congruent fashion. By joining the respective nxe2x88x921 coincident cut edges, a polygonal cushion similar to the two-panel cushion of the first embodiment may be formed, but without the need for a joining operation along the shared side due to the lack of any cut edge.
The polygon shapes can be placed in close proximity to one another on the fabric blank from which they are cut, thus minimizing fabric waste and cost, and providing a useful advancement over the present art. The fabric between polygon-shaped panels (the inter-panel fabric) tends to have straight sides and is therefore easier to utilize in the manufacture of other air bag components (e.g., reinforcements or other components). The advantages of the present invention include better fabric utilization and an overall simplification of the manufacturing process. By providing congruent polygonal fabric panels having linear edge segments, this invention facilitates seaming operations by improving in the ease, effectiveness, and efficiency with which the cut pieces can be aligned and joined during the seam formation process. Prior designs tend either to result in relatively poor material utilization due to the use of unusual panel shapes or to require more complex aligning, folding or sewing operations during the seaming process than is found in the instant invention. Accordingly, cost is lowered due to the improved yield per fabric blank as well as the increased efficiency with which the cutting and joining operations can be performed.
All of these advantages apply to the embodiment using two separate n-sided congruent polygon panels as well to the embodiment using a single, dual-lobed panel, with congruent lobes in the shape of the same n-sided polygon. However, an additional advantage of the latter embodiment of this invention is the additional simplification in cutting and sewing operations this embodiment provides. Because of the common uncut boundary shared by the n-sided polygons comprising the lobes, the number of coincident perimeter panel edges requiring joining (after the panel is folded and the lobes are superimposed in congruent fashion) generally is equal to nxe2x88x921. Sewing along the entire length of the perimeter of the finished air bag is not required, due to the presence of an intact section of fabric that forms an uncut transition between the respective lobes that become the face and rear panels of the air bag after the panel is folded along an axis coinciding with the common uncut side between the two polygonal lobes and the two lobes are superimposed in congruent fashion. This folding operation causes the respective cut edges of each lobe to coincide, thereby forming a layered, n-sided polygon having only nxe2x88x921 cut sides. Sewing is required on only the nxe2x88x921 cut sides of the folded panel, where n is the number of sides in each polygonal lobe. Each reduction in the number of sewn seams reduces the opportunity for rupture along a seam area, and reduces the number of necessary manufacturing steps.
Accordingly, this invention, in each of its embodiments, is believed to represent a useful advancement over the present art.
In view of the foregoing, it is an object of this invention to provide an air bag that can be formed from fabric panels that are cut from a fabric blank with a minimum amount of wasted fabric. The blank may be of woven or non-woven fabrics, films, or combinations or composites thereof, as may be prescribed by those skilled in the art.
It is another object of this invention to provide a vehicle occupant restraint cushion or air bag that can be formed from two polygonal panels, or from a single panel comprised of two abutting polygonal lobes, without the need for any additional attachments, shape-forming members, or reinforcements to define the surface of the air bag.
It is yet another object of this invention to provide an inflatable restraint cushion that, in one embodiment, is comprised of two congruent polygonal-shaped fabric panels in the shape of the same n-sided equiangular polygon, where n is at least five. The panels are superimposed and aligned in congruent fashion to make the n edges coincident. The edges are then joined along their respective n cut sides by a perimeter seam comprised of a series of easily-sewn or joined straight seams, with no need to fold either of the panels prior to the formation of the perimeter seam, and no need to orient the perimeter seam with respect to any fold line that may be used to facilitate storage of the uninflated air bag in an operative position within the vehicle.
It is still another object of this invention to provide an inflatable restraint cushion that, in another embodiment, is comprised of a single panel of fabric comprised of two congruent polygonal lobes that share a common uncut side. The two polygonal lobes are each in the shape of the same n-sided equiangular polygon, where n is at least five, i.e., each lobe is configured in the shape of a pentagon, hexagon, heptagon, octagon, or the like, each lobe having nxe2x88x921 cut sides. During assembly of the air bag, the two lobes are folded along an axis coinciding with the uncut n side shared by the two polygons, and superimposed to form a flat, layered, polygonal structure with an aligned, congruent perimeter comprised of n straight sides, of which nxe2x88x921 are comprised of coincident cut edges. The folded polygonal structure is seamed or otherwise joined together along the nxe2x88x921 cut sides by sewing or other suitable techniques. Because the shared side of the polygonal structure comprising the nth side is uncut fabric, seaming along this side may be regarded as optional. Although seaming operations usually use sewing, it is contemplated that if coated or other suitable fabrics are used, the coincident cut edges of the two lobes can be welded or otherwise secured together by techniques known to those skilled in the art.
Applicable to both embodiments, it is contemplated that additional layers of fabric or other materials may be interposed or placed alongside one or both of the layers, either fully or partially, as the specific design may dictate. Upon appropriate inflation, the resulting flat cavity will form a restraint cushion or air bag that, when incorporated into an appropriate air bag system, is suitable for protecting the occupants of a vehicle involved in a collision.
In accordance with one aspect of the present invention, a method for forming the inflatable cushion of the present invention from two separate polygon-shaped panels is provided. This method comprises the steps of: (a) cutting from a fabric blank a first fabric panel in a chosen n-sided equiangular polygon shape; (b) cutting from a fabric blank a second fabric panel in a congruent n-sided equiangular polygon shape; (c) superimposing the first and second panels in congruent fashion, thereby forming an n-sided, layered polygonal structure in which the respective n cut sides of each polygon are coincident, and (d) joining or sealing together the coincident cut sides along each of the n sides of the polygonal structure
In accordance with another aspect of the present invention, a method for forming the inflatable cushion of the present invention from a single panel is provided. This method comprises the steps of: (a) cutting from a fabric blank a single panel having a dual-lobed shape comprised of a pair of congruent, n-sided equiangular polygons that share a common uncut side, each lobe thereby having the shape of a polygon having nxe2x88x921 cut sides and an nth uncut side along which it is seamlessly joined to the other lobe; (b) folding this dual-lobed panel along an axis that coincides with the uncut nth side shared by the pair of polygons, thereby forming a layered polygonal structure in which the two polygonal lobes are superimposed in congruent fashion, thereby aligning each of the nxe2x88x921 cut sides of each lobe with the corresponding cut side of the other lobe to form a perimeter substantially comprised of a layered edge in which the nxe2x88x921 cut sides are coincident; and (c) forming a perimeter seam along each of the respective nxe2x88x921 cut sides.
Both the cutting and sealing operations may be achieved by manual, automated, or any other methods known by those skilled in the art. As is conventionally done, suitable holes may be cut in the rear panel or lobe to form gas inlet means, gas vents, or for other purposes. It should be noted that various other structural devices or reinforcements may be incorporated into the design of the air bag which may result in the resulting polygonal structure or cushion having more than two layers.